India must act right away against an emerging scarcity of fresh water

But there is a fourth fundamental challenge which will also have a profound effect on our lives in India and around the world—namely, the emerging global water crisis. Or to put it more precisely, the crisis of scarce fresh water supply. This column addresses this issue.

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To put things in perspective, here are some numbers. There is no scarcity of water per se. Accounting for over 70% of the earth’s surface, the world’s stock of water has been estimated at over 1.4 billion cubic kilometres—vastly in excess of our needs today and in the foreseeable future. However, only 2.5% of this is fresh water, mostly in the form of frozen polar ice-caps and glaciers (69%) and ground water (30%).

Only 1% is available as surface water, mostly as ground ice or permafrost and in lakes, marshes, rivers, living creatures and as water vapour in the atmosphere. The natural supply of fresh water is not only not growing, but is likely to shrink due to climate change.

Meanwhile, the consumption of fresh water has increased by 600% during the past century due to population growth and increasingly intensive fresh water use in agriculture, which accounts for 70% of total consumption, industry (23%) and home consumption (7%).

Large parts of the world are already water stressed and it is estimated that by 2030, demand for fresh water will exceed sustainable supply by 40%. This is the scale of the crisis.

The water crisis within India is a more granular though magnified version of the global picture. In my Mint column of 20 August 2021, which discussed what could be done to address the crisis on the demand side, I had pointed out that water tables have declined precipitously, even by thousands of feet in some parts of Punjab, Haryana and Andhra Pradesh.

Some rivers have shrunk while other smaller ones have dried up, as have many wells and tanks. Water rationing is routine in many urban areas, while in many villages, women are trudging longer distances to fetch water.

My Mint column had discussed how the crisis could be addressed on the demand side, especially conservation measures in agriculture, which accounts for 90% of water consumption in India. However, there are limits to what can be achieved by addressing only the demand side.

Today’s column focuses on the supply side. The growing demand for fresh water can only be met through increased production of fresh water.

There are a number of technologies already available for de-salination of water, mainly sea water. The traditional method of de-salination was distillation, where water was allowed to evaporate and then condensed to extract the desalinated water.

A modern version of this technology, multi-stage flash distillation, is one of the two main technologies currently used to desalinate sea water. Water is made to evaporate in a flash and the energy released during condensation is used to power the next cycle of evaporation-condensation.

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The other main technology in use is reverse osmosis (RO), where saline water is forced through a semi-permeable membrane that traps the salt, releasing fresh water on the other side. Many readers will be familiar with RO systems used at home to purify water.

Both flash distillation and RO are very energy intensive, but RO requires less power than flash distillation. RO is also the fastest spreading technology for desalination. Both technologies can be solar-power based, which would make them carbon neutral, but they are still very costly because of their high energy intensity.

Energy cost accounts for about half the cost of desalination. Though some 177 countries have desalination plants, including India (in Chennai), this purification method has not really taken off because of its high energy cost. The exceptions are the water-scarce countries of North Africa and West Asia, especially Saudi Arabia, Israel and the United Arab Emirates, and island economies that lack natural fresh water supply.

However, energy costs and hence the cost of desalination are declining rapidly. The cost of 1 cubic metre of desalinated water has come down from over $1 in 2000 to less than $0.40 now, according to some estimates. With the growing gap between demand and supply of fresh water, and rapidly declining costs, the spread of desalination is beginning to gather momentum.

Many cities in India and large parts of rural India are already facing severe water scarcity. However, India is also lucky in having a huge coastline of over 7000km along the national mainland and around its islands, which offers vast potential for producing desalinated fresh water. That potential is yet to be utilized. But if we are to avoid a severe water crisis 10 or 20 years down the road, the time to act is now.

Also read: The depth of India’s water crisis, explained in charts

In its two terms in power at the Centre, the Modi government has laid great emphasis on investment in infrastructure, mainly for transport, power and communications. As the government launches into its third term, it is a good time to add desalination to this investment portfolio.

These are the author’s personal views.

The author is chairman, Centre for Development Studies.